Sydney airport back to normal

Operations have returned to normal at a Sydney Airport terminal that was evacuated after a security breach.

Hundreds of passengers, airline staff, retail and support workers were forced from domestic Terminal 3, operated by Qantas, after a group of passengers from Armidale entered a "sterile area" without being screened on Tuesday afternoon, a Qantas spokeswoman said.

"Terminal operations are now back to normal," she told AAP.

"There was a short turnaround, with the clearing of the terminal commencing at around 2pm (AEST), and re-screening commencing at 2.30 pm."

Passengers alighting from the Armidale-to-Sydney flight should have been directed to a special exit, as there are no security screening facilities at the regional airport.

Instead they were allowed into an area beyond Terminal 3's screening points, causing Qantas to follow its security policy, which involved emptying the terminal and rechecking passengers.